To obtain improved engine power to displacement for improved vehicle driveability, turbo charging, or supercharging has been used. In this system, engine performance is increased by compressing air entering and engine intake manifold, thereby forcing more air into an engine cylinder. The engine then produces increased engine torque. Such an approach is advantageous in improving vehicle fuel economy by reducing engine size and weight while obtaining equal maximum engine performance.
The inventors herein have found a disadvantage with the above approach. In particular, the phenomena known as “turbo lag” degrades drive performance during transient driver commands. For example, at lower engine speeds and low engine torques, when a driver requests a rapid increase in torque, there is a delay since the turbo charger first builds up speed and the engine manifold then builds pressure. These combined delays produce “turbo lag”.